This invention relates to a method for coating a surface with an atomizable material. More specifically, it relates to a method for providing a uniform coating of a material containing particulate matter entrained therein, as for instance a slurry. A slurry comprises solid particles in a liquid wherein the solids fraction is reasonably high, i.e. has a significant effect on the flow dynamics of the liquid.
In a known configuration, as shown in FIG. 1 of my above-identified co-pending application Ser. No. 345,509, the material to be atomized is fed to a surface of a rotating disk assembly through a passageway. The walls of the passageway are generally an integral part of the rotating disk assembly and rotate with it. Thus a rotation or swirl is imparted to the material as it flows through the passageway. A seal is required to interface between the rotating portion of the apparatus and the non-rotating source of the material to be atomized. If this material, as in the case of a slurry, contains particulate matter, then the seal is subject to wear and abrasion from the particulate matter, especially if a high speed of rotation, e.g. greater than 20,000 RPM, is required. Also, the swirling induced in the material may cause surface waves at the receiving surface of the rotating disk, thus causing an uneven flow of material across the surface of the disk with a resulting loss of uniformity of size of the droplets formed. Further, if the material contains particulate matter, forces induced in the passageway may cause the particulate matter to selectively segregate, especially where the particulate matter comprises particles having different densities and shapes, thus destroying the uniform mix of the material.
In another known configuration, as shown in FIG. 2 of my above identified co-pending application Ser. No. 345,509, the material to be atomized is delivered to a surface of a rotating disk from a direction which is on the opposite side of the disk from the drive means. Thus at least a portion of the material delivery means is located generally in the path of droplets moving axially away from the surface of the rotating disk. In certain applications, it is desirable that the droplets move axially away from the rotating surface and in these cases such positioning of the delivery means would interfere with this flow of the droplets. Also, geometric and space considerations may limit such positioning of the delivery means.